The invention concerns a device for providing circulation in pump stations which are included as part of a municipal sewage system.
As is described in U.S. Pat. No. 4,462,766, issued July 31, 1984, sludge banks occur in pump stations and other tanks in a sewage system due to poor circulation. A sludge bank can cause a number of problems, including bad odors, risk of explosions, corrosion problems, etc. As indicated in Swedish Patent Application No. 7908743-3, the problems have been solved by arranging a valve in the pump outlet. The valve is opened temporarily to obtain a circulation and flushing in the pump station, causing the sludge banks to be dissolved and the fluid homogenized.
The adjustment of the valve has up to now been electrically controlled by means of a linear motor which acts upon a slide in the valve. A disadvantage with this solution, in addition to its relatively high cost, is that it may easily become clogged as the pumped medium normally contains large amounts of solid bodies such as stones, rags and other objects. If a stone becomes stuck in the valve slide, the electric motor may stall and burn out or break down.